Hi Johnny, Many thanks - your suggested fix of a new kernel works perfectly! My Opterons are happy once more :) Also - thanks Joshua for your advice: I last tried x86_64 with Whitebox 3, and had many problems with VMD, InsightII, Xeasy and MolMol - I'll have a go at 64bit again soon - has your 64bit experience been painless ? Jake Problem was: >Centos 4.2 i386 version caused smp Opteron workstations with Nvidia graphics > cards to, nine times out of ten, hang when they try to re-load > X... and just sitting there with the Caps and Scroll lock LED's > flashing. only way out is the reset button. > Jake, > > There is a new kernel that addresses this specific issue that has just > been released. (2.6.9-22.0.1.EL) > > I am building it now, but the kernel updates take quite some time. > Should be done later to day though. > > -- Dr J. Grimmett Computer Systems Manager Division of Molecular Structure National Institute for Medical Research The Ridgeway Mill Hill London, NW7 1AA Tel: 0208 816 2028 Fax: 0208 906 4477